We want to serve our files from Amazon S3.

We are worried about cost DoS attacks (deliberately downloading files from Amazon many times, in order for us to pay a big bill to Amazon).

We don't have enough money to use AWS Shield Advanced now.

Question: Will serving S3 not directly but through CloudFront help to reduce possible cost attacks? How much (if any) does it help against cost attacks?

1 Answer 1


A user or bots downloading the same file again and again is not a DOS attack. Cloudflare provides unmetered DOS attacks:

Cloudflare’s unmetered mitigation of DDoS stops illegitimate volumetric traffic at the Cloudflare edge. All Cloudflare plans include unmetered mitigation without fear of being dropped.

Cloudflare will cache these file formats and up to 512MB a file for Free, Pro and Business accounts.

Cloudflare will reduce your server-side traffic from around 50-75% and will vary depending on your traffic, page rules and how your site is built and what it hosts.

If your expecting an approximate saving then you will be waiting a long time since no one will be able to answer that.

  • Cloudflare also puts a check on suspicious behaviour. Plus, even if a user (or bot) downloads the same file over and over it should be cached but that depends on your web server setup specifics - it is fairly straightforward to almost force caching or deny caching of particular resources in most cases.
    – Willtech
    May 21, 2018 at 13:19

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